Remove PEP-604 methods from `Sentinel` on Python <3.10 (#605) #2061

Job	Run time
Lint	8s
Run tests (3.9)	6s
Run tests (3.9.12)	12s
Run tests (3.10)	5s
Run tests (3.10.4)	14s
Run tests (3.11)	6s
Run tests (3.11.0)	13s
Run tests (3.12)	9s
Run tests (3.12.0)	12s
Run tests (3.13)	5s
Run tests (3.13.0)	14s
Run tests (3.14)	14s
Run tests (pypy3.9)	9s
Run tests (pypy3.10)	6s
Create an issue if daily tests failed	0s
	2m 13s

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